Crystal polycrystal

An extension of the kinetic theory on cases when a mechanical pressure interacts with kinetic processes inside solid volume and on interfaces has wide application interests. The elastic deformations in solid are presented from influence of external forces and from presence of internal defects of crystal structure point defects (vacancy, intersite atoms, complexes of atoms, etc.), extended defects (dislocations and inner interfaces in polycrystals), and three-dimensional defects (heterophases crystals, polycrystals). 

A diamond tool design is dependent on both diamond toughness and hardness properties and plays a role in the G ratio, which is defined as the volume of material removed over volume of tool worn. Toughness describes the way diamond fractures during use. It is also known as friability. Hardness describes diamond s resistance to abrasion and is also known as scratch and indentation. Its value ranges from 57 to 104GPa and depends on crystal orientation, e.g., (100) and (111) surfaces, respectively, for single crystals. Polycrystal-line diamonds have no orientation dependence for hardness parameters because of the statistical nature of surface orientation. A bulk value for hardness is used instead. 

The TSC method was first developed by Bucci and Fieschi in 1964 (15). The technique was initially used to characterize point defects in simple crystals. Later, it was applied to a wide variety of samples, including inorganic materials (insulators as halide crystals, polycrystals, or amorphous materials semiconductors in crystalline or amorphous state), or organic materials (small molecules in noncrystalline or crystalline states, amorphous or semicrystalline synthetic macromolecules, and natural macromolecules) (12-14). 

Figure 3.12. HREM images of the boundaries between a single crystal and a fine matrix grain. (100) single crystal/polycrystal bi-layer samples with 0.4-mol%-TiO2 addition annealed at I350°C for (a) 5, (b) 20, and (c) 50 h in air after H2-treatment at I250°C for 10 h. ...

P.S. Follansbee and G.T. Gray III, The Response of Single Crystal and Polycrystal Nickel to Quasi-Static and Shock Deformation, in Advances in Plasticity 1989 (edited by A.S. Khan and M. Tokuda), Pergamon Press, Oxford, 1989, pp. 385-388. 

The crystals, or grains, in a polycrystal fit together exactly but their crystal orientations differ (Fig. 10.4). Where they meet, at grain boundaries, the crystal structure is disturbed, but the atomic bonds across the boundary are numerous and strong enough that the boundaries do not usually weaken the material. 

As the stress is reduced, the rate of power-law creep (eqn. (19.1)) falls quickly (remember n is between 3 and 8). But creep does not stop instead, an alternative mechanism takes over. As Fig. 19.4 shows, a polycrystal can extend in response to the applied stress, ct, by grain elongation here, cr acts again as a mechanical driving force but, this time atoms diffuse from one set of the grain faces to the other, and dislocations are not involved. At high T/Tm, this diffusion takes place through the crystal itself, that... 

TEM offers two methods of specimen observation, diffraction mode and image mode. In diffraction mode, an electron diffraction pattern is obtained on the fluorescent screen, originating from the sample area illuminated by the electron beam. The diffraction pattern is entirely equivalent to an X-ray diffraction pattern a single crystal will produce a spot pattern on the screen, a polycrystal will produce a powder or ring pattern (assuming the illuminated area includes a sufficient quantity of crystallites), and a glassy or amorphous material will produce a series of diffuse halos. 

D. Goldberg, G. Sauthoff. Effect of ageing at 673 K on the compressive behaviour of <110> oriented ("soft") NiAl single crystals and polycrystals with and without Ti additions, Intermetallics 4 143 (1996)... 

Using single crystals it has been shown that different low-index crystal faces see Section 20) exhibit different corrosion rates. However, the relative corrosion rate of the different faces varies with the environment and these structural effects are of little practical significance. On the other hand, the fact that polycrystal grains of different crystallographic orientation may corrode at different rates, is of some importance. 

Yield Stress The effect of hydrogen on the yield stress of iron and steels is unpredictable. For very pure iron single crystals and polycrystals the yield stress is frequently found to be decreased by hydrogen, but it may increase or stay the same, depending on the dislocation structure, crystal orientation and purity of the iron . Little information is available for steels. 

Crystal structure Single crystal and polycrystal, single crystal appearing as cubiccrystal structure, and lattice constant is 0.3559-0.3570 nm. 

Semiconductor adsorbents used as operational elements in sensors can be monocrystals or monocrystal films as well as polycrystals. The latter can be arbitrary divided into two groups differing in properties of contacts between monocrystals. The first group contains those polycrystal line adsorbents in which contacts between crystals can be represented as a double Shottky barrier or, in more general case, isotype hetero-... 

Tetragonal structure, of ferroelectric crystals, 11 95, 96 Tetragonal symmetry, 8 114t Tetragonal zirconia polycrystals, 5 571 Tetrahedral... 

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